The invention relates to a spinning machine having a plurality of spinning positions and having a package spool changing arrangement or doffing arrangement which can be moved along the spinning machine. The doffing arrangement can be applied to the individual spinning positions and is equipped with devices for removing a full X-package out of a cradle of a spinning position and with devices for inserting an empty tube at the spinning position. Each spinning position is provided with devices for detecting a predetermined degree of fullness of the X-package and for interrupting the spinning operation of this spinning position.
In the case of spinning machines of the initially mentioned type, it is generally customary that, also when the spinning position is stopped, the yarn is wound onto the X-package while maintaining the cross-winding so that the yarn end may be situated at any arbitrary point of the X-package. The yarn end must then be found for a subsequent processing step of the X-package in which the yarn is again removed from the X-package. This operation may be connected with considerable difficulties, particularly if the circumference of the package is subjected to transport stress. These difficulties occur mainly in the case of fine yarns and particularly also in the case of X-packages wherein two yarns were wound onto the X-package as a double yarn. It will then frequently be difficult to grip the yarn ends of the two individual yarns simultaneously and in a sufficiently secure manner. In particular, it may happen during the transporting of the X-package that the ends of the two yarns separate from one another and will then be situated at different points on the X-package.
It is an object of the invention to develop a spinning machine of the initially mentioned type such that a later finding of the yarn end or yarn ends on the X-package is facilitated.
This object is achieved in that the doffing arrangement comprises devices for the winding-off of the yarn wound onto the full X-package and for winding this yarn back onto a predetermined area of the X-package in parallel layers and/or layers disposed above one another.
As a result of the inventive arrangement, it is achieved that the yarn end comes to be situated at a defined point of the X-package so that it can be picked up again relatively easily. Since the picking-up is normally carried out by means of a suction nozzle, this suction nozzle must only be aligned to the predetermined area of the X-package. This is advantageous particularly in the case of X-packages onto which a sensitive yarn was wound, for example, a double yarn formed from only prestrengthened individual yarns, where there is the danger that a strong suction pull of the suction device may damage the yarns.
In a further development of the invention, it is provided that each spinning position is equipped with devices for holding the yarn end formed during the interruption which are arranged at a distance from a cradle for the X-package. As a result, it is ensured that, also during the winding-off to be carried out by the doffing arrangement, the yarn end can be found very easily because it is held to be available at a point away from the X-package. This prevents that the yarn end, during the stopping, is pressed into the outer circumference of the X-package and will then be hard to find and to detach.
In a further development of the invention, it is provided that the devices for the holding have a suction device. In an advantageous manner, this suction device may then also be used to first store the yarn length wound off during the winding-off by means of the doffing arrangement and then release it during the rewinding which follows.
In another development of the invention, it is provided that each spinning position is equipped with devices for taking the yarn out of a cross-winding device which is part of the spinning position, in which case, these devices can be operated during the interruption of the spinning operation when a predetermined degree of fullness of the X-package is reached. This ensures that, after the interruption of the spinning operation, the yarn, on the one hand, is not subjected to stress by the cross-winding device while, on the other hand, it is also ensured that the cross-winding device is bypassed during the rewinding carried out by the doffing arrangement.
In a further development of the invention, it is provided that each spinning position, which is equipped with devices for spinning two individual yarns and for guiding the individual yarns together to form a double yarn, is provided with devices for strengthening the double yarn which can be operated during the interruption of the spinning operation when a predetermined degree of fullness of the X-package is reached. Thus it is achieved, particularly for X-packages with double yarns consisting of only prestrengthened individual yarns, that for the subsequent operation, particularly for a twisting, a uniform and relatively firm yarn end is available which is easier to grip and to be subjected to threading operations or the like.
In another development of the operation, it is provided that the doffing arrangement is equipped with devices for the strengthening of the yarn which, after being wound off, must again be wound up onto the X-package. Also this development may particularly advantageously be used during the producing of X-packages with double yarns consisting of only prestrengthened individual yarns. This strengthening may take place in that the two individual yarns are strengthened by means of swirling-together or winding-around or by adding a strengthening medium. In this case, an auxiliary yarn, particularly a filament yarn, may also be added which causes the strengthening. It is also possible to carry the strengthening out in such a manner that a spun or twisted auxiliary yarn which has a clearly higher strength is pieced to the yarn end and thus can be manipulated with the risk of yarn breakages being lower.
In a further development of the invention, it is provided that the doffing arrangement is equipped with devices for cutting into lengths the yarn which is to be wound back onto the X-package. This achieves, on the one hand, that a precisely determined length is wound up at the predetermined area while, on the other hand, a defined end of the yarn is produced; i.e., that, particularly in the case of a double yarn, the ends of the two individual yarns come to be situated at the same point and the individual yarns also have the same length.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.